altering the bp-blogs-widget

i want to place the buddypress profile avatar before the username in the widget “recent sitewide posts”. So i achieved this by altering the bp-blogs-widget.php file. But i think it will create problem while updating. so can anyone help me in this regard? i think child theme concept will help. i know a little about creating child theme. can anyone guide me in altering the above said file in child theme?